An intake apparatus for an internal combustion engine is known from e.g. U.S. Pat. No. 6,138,628.
The intake apparatus for an internal combustion engine disclosed in this patent comprises an intake manifold and a camshaft controller disposed within this intake manifold.
The intake manifold forms a plurality of air feeding passages with individual induction tubes and shorter individual induction tubes for respectively feeding air to a plurality of cylinders of the internal combustion engine.
The camshaft controller includes a plurality of portions that have openings and that are rotatable together. Each portion is operable to open and close an individual induction tube associated therewith.
Each portion of the camshaft controller includes a sealing cage. This sealing cage includes a pair of ring elements and sealing bars connecting the pair of ring elements to each other. Each ring element is fitted within a groove located at a corresponding end of the valve portion.
This type of intake apparatus has an arrangement whose general principle is illustrated in FIGS. 14(a) and 14(b). It is to be understood that FIGS. 14(a), 14(b) and the description here are provided for the sole purpose of illustrating the operational principles of prior art and that they do not constitute any admission as to prior disclosure of specific configurations of the apparatus. These figures show how the feed switch opening 7 is closed by a valve portion 11.
As shown, each of the interconnecting portions 62 of a sealing member 60 has an engaging portion 64 disposed on the inner side. Each engaging portion 64 is received by a corresponding recessed portion 76 disposed on the outer peripheral side of the valve portion 11.
A sealing gap E is provided between each engaging portion 64 and an inner face portion 77 of the corresponding recessed portion 76. The inner face portion 77 is located on the side opposite from the other side where the feed switch opening 7 of the intake manifold 1 is located, relative to the engaging portion 64, when the feed switch portion 7 is closed by the valve portion 11.
In general, the valve portions 11 and the sealing members 60 are formed by resin molding. Therefore, if the sealing gap E is small, a engaging portion 64 may come into contact with the corresponding inner face portion 77 of the recessed portion 76 due to manufacturing variations in the valve portions 11 and the sealing members 60. When this happens, the interconnecting portion 62 will be pressed against a bore portion 8, which results in an increase in resistance in the switching operation of the valve portion 11. Therefore, the sealing gap E is configured so as to avoid such contact between the engaging portions 64 and the inner face portions 77, regardless of the manufacturing variations in the valve portions 11 and the sealing members 60.
For this reason, the sealing gap E was conventionally set larger than a valve gap C provided between the outer peripheral edge 15a of each valve portion 11 and the bore portion 8.
In addition, the inner surface of the bore portion 8 and the outer peripheral edge 15a were conventionally arc-shaped and coaxial with their center at the rotational center P of the valve portions 11. A result was a problem illustrated in FIG. 14(b).
Specifically, when the rotary valve is switched to the closed position so that the valve portions 11 close the feed switch openings 7, the rotary valve starts to vibrate due to e.g. pulsation of intake air generated in the air feeding passages caused by operation of the internal combustion engine. As a result, the rotary valve will be deformed such that the valve portions 11 are repeatedly displaced toward and away from the respective feed switch openings 7. The displacement of a valve portion 11 toward the corresponding feed switch opening 7 causes movement of the valve portion 11 relative to the sealing member 60, which leads eventually to collisions of the outer peripheral edge of the valve portion 11 against the bore portion 8 in the vicinity of the feed switch opening 7, thus casing a collision noise.